The invention relates to weightlifting apparatus such as those involving barbells with free-weights or those involving stacked weight machines. In particular, the invention relates to weightlifting apparatus which can be safely used without the aid of a spotter.
Weightlifting without a spotter on an apparatus which requires a spotter, is dangerous. For example, weightlifters often exercise by performing many repetitions of the same weight through a point of partial muscle failure. Since assistance must be provided to continue beyond the point of partial muscle failure, this exercise requires that a spotter be present at all times.
Conventional weightlifting apparatus which do not require the assistance of a spotter include apparatus which provide a power source to protect a user in response to a switch under the control of, and actuated by, the user (U.S. Pat. No. 4,253,662). Weightlifting apparatus which provide a power source to protect a user are superior to other weightlifting apparatus in their ability to safely protect an extremely fatigued weightlifter. Such prior art power assist apparatus, however, have the disadvantage that the extremely fatigued user must locate and actuate the user operated switch. If either of these activities (locating the switch or actuating the switch) cannot be accomplished, then the fatigued weightlifter is likely to be in serious danger.
Conventional weightlifting apparatus which provide automated safety capabilities include U.S. Pat. No. 4,807,875 to Tanski. Such apparatus typically take control of the weight being lifted once a trouble signal has been activated. Such apparatus, however, do not provide intermittent spotting capabilities to varying degrees allowing a weightlifter to continue performing many repetitions after muscle failure has occurred. A weightlifter may desire to continue performing a set of repetitions after he or she has needed assistance, even if he or she only contributes a small portion of the force needed to lift the weight each time. A person spotting such a weightlifter would be able to provide such intermittent spotting assistance. A weightlifting apparatus with automated safety capabilities, however, is not able to accomplish this.
It is therefore an objective of the present invention to provide for a power assist weightlifting apparatus which provides intermittent spotting capabilities, allowing a weightlifter to continue performing repetitions during partial muscle failure.